Technical Field
The present invention generally relates to semiconductor transistors. More particularly, the present invention relates to fabricating a FinFET on a bulk semiconductor substrate with a dielectric layer directly under the active region.
Background Information
Fin field-effect transistors (FinFET) devices have been developed to replace conventional planar bulk MOSFETs in advanced CMOS technology due to their improved short-channel effect immunity and Ion/Ioff ratio. However, a problem with bulk FinFET devices is that a leakage path from source to drain exists through a portion of the fin not covered by the gate, but lies below the channel. The leakage of current from source to drain through the lower (un-gated) part of the fin, commonly known as punch-through leakage, causes an increase of static power consumption which is undesirable in modern submicron devices.
In one solution, punch-through leakage in submicron semiconductor devices is sought to be controlled by implanting a punch-through-stopper (PTS) dopant in a portion of the fin directly below the channel. However, the impurities doped by the punch-through-stopper (PTS) implantation may diffuse into the channel region, increasing the variability due to random dopant fluctuation (RDF) and lowering the carrier mobility of the channel region.
Thus there continues to be a need for a solution to the punch-through leakage problem.